The present invention relates to a laser scanner for acquiring three-dimensional data of an object to be measured by projecting a distance measuring light to the object to be measured, by measuring a distance to the object to be measured after receiving a light reflected from the object, and by detecting a projecting direction of the distance measuring light when measurement is made.
A type of laser scanner is known, by which it is possible to perform measurement at a multiple of points on an object to be measured. The laser scanner projects a pulsed laser beam as a distance measuring light and scans over a measurement area as required including an object to be measured and measures a distance by receiving a light reflected from the object to be measured for each pulsed laser beam, and acquires three-dimensional data by detecting a direction (i.e. horizontal angle and elevation angle) of the pulsed laser beam at the time of distance measurement.
When measurement is performed by using the laser scanner, it is necessary to set up a range to be measured, i.e. a range, to which a pulsed laser beam is projected for scanning. In the past, it has been practiced to connect an external control system such as a personal computer (PC) to the laser scanner. It has been practiced to set up a measurement range by inputting numerical values of horizontal angles and vertical angles on points to designate and define the measurement range, e.g. four points in the case where the measurement range is in form of a rectangle.
In the case the measurement range is set up by inputting numerical values, an operator of the measurement cannot numerically recognize as to in which direction the object to be measured is positioned with respect to the laser scanner. For this reason, the inputting of numerical values and the measurement had to be repeatedly performed, and the final measurement range had to be set up through repeated trials and errors.
Alternatively, in the case the laser scanner is provided with an image pickup device, an image of visual field acquired by the image pickup device can be displayed on a display unit of the PC, and the measurement range can be set up on the image on the PC. When the image is incorporated into the PC from the laser scanner, numerical values on a range to be incorporated must be set up again from the PC, and complicated procedures cannot be avoided. In this respect, it is necessary to acquire an image, which is far wider and extensive than the measurement range itself, and this means that much time is needed for acquiring the image.